PROCEEDINGS OF ECOS 2015 - THE 28 TH INTERNATIONAL CONFERENCE ON EFFICIENCY, COST, OPTIMIZATION, SIMULATION AND ENVIRONMENTAL IMPACT OF ENERGY SYSTEMS JUNE 30-JULY 3, 2015, PAU, FRANCE 1 Heat Integration Assessment for the Conceptual Plant Design of Synthetic Natural Gas Production from Supercritical Water Gasification of Spirulina Algae Mohamed Magdeldin a , Thomas Kohl a , Cataldo De Blasio a , Mika Järvinen a a Department of Energy Technology, Aalto University School of Engineering, FI-00076 Aalto, Finland, mohamed.magd@aalto.fi Abstract: Hydrothermal processing of biomass, and in particular supercritical water gasification, SCWG, has illustrated the potential to counter technical barriers that continue to face the wide deployment of biomass based energy systems. A conceptual plant flow sheet for SCWG of spirulina algae feedstock is developed on Aspen plus® for synthetic natural gas production. The advantageous reactor system configuration at 600˚C for higher organic conversion, nutrient separation and the energetic polygeneration of chemical fuels, electricity and thermal heat, is integrated in the process layout with subsequent gas purification, mechanical power extraction and a downstream methanation reactor for indirect production. The design and synthesis for the process blocks, components and equipment was based on operational data for referenced pilot or commercial units, and the pinch analysis method was used to assess the minimum plant utility demand as well as develop the heat exchanger network. 60.7% and 46.9% were recorded for the overall energetic and exergetic evaluation of the plant respectively. An alternative plant design was assessed at a reactor temperature of 450˚C to favour direct methane production from the SCWG reactor and with the exclusion of mechanical power extraction for better heat recovery. The alternative design recorded energetic and exergetic efficiencies of 68.9% and 57.4% respectively. Keywords: Supercritical water gasification, SCWG; Spirulina algae; Conceptual process design; Pinch analysis; Synthetic Natural Gas, SNG. 1. Introduction The deployment of renewable energy systems continues to grow as a priority globally. The current urgency to break the dependence on fossil fuel based energy production, and curb continued rise of green-house emissions while developing sustainable energy supply chains is considered the main motivation within scientific, industrial and governance circles. As a result biomass is predicted to play a key role within the intended future green global economy. Biomass feed stocks in particular offers distinctive advantages among the wide variety of available primary energy fuel sources. Holistic life cycle system design allows for production pathways to gaseous and liquid chemical fuel products while maintaining carbon dioxide emissions neutrality. In addition to, biomass offers continuous energy supply as base load for heat and power generation without the utilization of storage technologies in contrast to intermittent renewable sources such as solar and wind. [1] This research investigates the biomass gasification process, which is considered a thermo-chemical approach to valorise solid biomass. The produced fuel gas is known as synthetic gas or syngas and is a mixture of CH 4 , H 2 , CO x , N 2 and smaller quantities of heavier hydrocarbons. The technical barrier that continues to hold back the wide deployment of biomass gasification systems is the lowered conversion efficiency compared to other conventional systems. The produced syngas is